Pivotable knives have blades, the sharp edges of which engage the knife handle when in a closed position. Users of such knives are prone to place their fingers or hands between the blade and the blade engaging portion of the handle when opening or closing the knife blade. Such action increases the likelihood of accidentally cutting one's hands while pivoting the knife blade. Therefore, it is desirable to create a sheath in which the knife may be kept that will automatically retract and extend the knife blade as the knife is inserted and removed, respectively. Furthermore it is desirable to design a sheath that will automatically extend a knife blade without having to rotate the knife handle, as such action necessarily causes a person to grasp the knife handle with an unnatural and dangerous grip.
Prior art sheaths include those described in U.S. Pat. Nos. 4,466,561, 4,494,310, 4,389,775.